The waves inherently present in lakes, rivers, and oceans produce an unstable platform for boats travelling on such waterways. For many people, the rocking, lifting, and falling motion is unsettling and causes sea sickness. In some cases the motion is merely unpleasant, and for some it is sufficiently severe that sea travel is not possible.
Over the years, a variety of approaches have been pursued to incorporate some form of suspension into a boat, but with limited success. The suspension efforts have mainly been directed to forms of passive dampening of the pitch and roll experienced on the boat, with some systems being as simple as a seat on springs and other systems seeking to cushion the deck of the entire boat through the use of flexible arms, springs and shock absorbers.
One early approach is described in U.S. Pat. No. 2,347,959 for a “water spider.” This patent describes the use of four outrigger pontoons connected by a series of linkages to a vessel that is preferably in the form of a fuselage raised above the water. Spring-based shock absorbers are positioned in one or more of the linkages. In general, the objective of the '959 patent is to improve lateral stability while urging the fuselage in a generally horizontal position. This suspended fuselage configuration provided at least some measure of stability in the pitch and roll axes, but offered little in maintaining deck height.
Others have subsequently produced similar boats with suspension systems seeking to dampen pitch and roll in the platform of a boat. A further example is in U.S. Pat. No. 6,176,190 for a “suspension system for a speed boat.” In this patent, left, right, and vertical shock assemblies are positioned between the hull and the deck in an effort to dampen movement between the deck and the hull. As a general principle, the deck of the boat will rise and fall with the hull, with the dampening principally affecting pitch, roll, and yaw of the deck with respect to the hull.
A similar approach is described in U.S. Pat. No. 6,763,774 for an “active deck suspension system.” As with the above examples, this patent is concerned with shock absorption in the same manner as with the other prior art approaches, but incorporates pneumatic cylinders for damping forces imparted on the boat, using what it characterizes as active control of the suspension.
A common defect among prior art suspension systems incorporated into watercraft is that they generally do not account for all degrees of motion. Most are concerned only with pitch and roll, and none are truly able to maintain a constant deck height, or heave. While some systems can dampen an upward or downwardly directed force to some extent, the systems are only concerned with reducing the effect of the motion and none are directed toward maintaining a constant deck height. Moreover, prior art dampening systems that incorporate a vertical dampening vector tend to raise one region of a boat deck relative to another region. For example, in controlling roll one side of a deck is raised while the other side is fixed or lowered. There is generally no meaningful ability to maintain deck height by incorporating a significant amount of travel of the deck height with respect to the hull or pontoon position of the boat.
Some prior art suspension systems incorporated into boats employ fins that are controlled by gyroscopes to reduce the roll motion, and some of these are effective even when the boat is not moving. In some instances giant mechanical gyroscopes are mounted in a yoke to reduce the rolling motion of the boat. Boat hull design has also matured over the years to provide a degree of “sea keeping,” a term describing the levelness of the boat when under way.
But sea sickness remains a common complaint of the casual sailor, feared by so many individuals that it affects the popularity of many common boating outings, from whale watching to ferry service. And there is the less annoying, but still concerning, “sea legs” phenomenon where one feels like one is still rocking on the boat when back on solid ground. These ailments are a function of motion of the deck of the boat in any direction, including the heave direction as well as pitch, roll, and yaw. The prior art systems have managed to dampen some of these forces in certain sea conditions, but have not been particularly effective and have not addressed the control of the deck in the heave direction.